US8137857B2 - Liquid electrolyte fuel cell having an anode substrate layer thicker than the cathode substrate layer - Google Patents

Liquid electrolyte fuel cell having an anode substrate layer thicker than the cathode substrate layer Download PDF

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Publication number
US8137857B2
US8137857B2 US12/311,592 US31159206A US8137857B2 US 8137857 B2 US8137857 B2 US 8137857B2 US 31159206 A US31159206 A US 31159206A US 8137857 B2 US8137857 B2 US 8137857B2
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anode
cathode
fuel cell
substrate
catalyst
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US20090325033A1 (en
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Richard D. Breault
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UTC Power Corp
Hyaxiom Inc
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UTC Power Corp
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Assigned to DOOSAN FUEL CELL AMERICA, INC. reassignment DOOSAN FUEL CELL AMERICA, INC. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: CLEAREDGE POWER, INC., CLEAREDGE POWER, LLC, CLEAREDGE POWER INTERNATIONAL SERVICE, LLC
Assigned to HYAXIOM, INC. reassignment HYAXIOM, INC. CHANGE OF NAME (SEE DOCUMENT FOR DETAILS). Assignors: DOOSAN FUEL CELL AMERICA, INC.
Assigned to HYAXIOM, INC. reassignment HYAXIOM, INC. CORRECTIVE ASSIGNMENT TO CORRECT THE THE ASSIGNEE ADDRESS PREVIOUSLY RECORDED AT REEL: 059364 FRAME: 0046. ASSIGNOR(S) HEREBY CONFIRMS THE ASSIGNMENT. Assignors: DOOSAN FUEL CELL AMERICA, INC.
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/08—Fuel cells with aqueous electrolytes
    • H01M8/086—Phosphoric acid fuel cells [PAFC]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/86—Inert electrodes with catalytic activity, e.g. for fuel cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/02—Details
    • H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
    • H01M8/023—Porous and characterised by the material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04276—Arrangements for managing the electrolyte stream, e.g. heat exchange
    • H01M8/04283—Supply means of electrolyte to or in matrix-fuel cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04007—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids related to heat exchange
    • H01M8/04067—Heat exchange or temperature measuring elements, thermal insulation, e.g. heat pipes, heat pumps, fins
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Definitions

  • a liquid electrolyte fuel cell substrate layer adjacent to the anode catalyst (sometimes referred to as a gas diffusion layer, or GDL), is as much as three or four times thicker than the substrate adjacent to the cathode catalyst, to accommodate the preponderance of acid stored at the anode side of the fuel cell.
  • GDL gas diffusion layer
  • U.S. Pat. No. 4,374,906 shows a cell with ribbed anode and cathode substrates.
  • the '906 cell has a high acid inventory and good electrolyte management characteristics; but is expensive to manufacture due to the high content of expensive carbon fibers and the high volume of carbon-carbon composite material that must be heat treated.
  • U.S. Pat. No. 5,558,955 shows a cell with a ribbed electrolyte reservoir plate as the anode flow field and a nonporous hydrophobic cathode flow field.
  • the '955 cell also has a high acid inventory and good electrolyte management characteristics; but is still expensive to manufacture due to the high volume of carbon-carbon composite material that must be heat treated. Graphite flow fields are not acceptable because they absorb a significant quantity of acid and thus reduce the life of the fuel cell.
  • WO/2006/071232 discloses a cell which has nonporous anode and cathode flow fields and all of the acid must be stored within the hydrophilic electrode substrates.
  • This cell represents a lower cost design because the carbon fiber content is minimized and the volume of material that must be heat-treated is substantially reduced. Furthermore, porosity need not be a factor, since the flow fields are both non-porous.
  • the '232 cell has poorer electrolyte management characteristics which are the subject hereof.
  • Proton-conducting liquid electrolytes which may be used as alternatives to phosphoric acid are known.
  • U.S. Pat. No. 5,344,722 discloses an electrolyte which is a mixture of phosphoric acid and a fluorinated compound or a mixture of phosphoric acid and siloxanes.
  • U.S. Publication No. 2006/0027789 discloses a proton-conducting liquid electrolyte where the anion is a fluoroborate or fluoroheteroborate.
  • each fuel cell 8 comprises an acid retaining matrix 11 having anode catalysts 12 on one side and cathode catalysts 13 on the other side.
  • the catalysts are respectively supported by a porous anode substrate 16 and a porous cathode substrate 17 .
  • Porous anode substrate 16 and porous cathode substrate 17 are hydrophilic as is known in the art.
  • the fuel cells (except at the ends or adjacent to cooler plates) share non-porous, hydrophobic separator plate assemblies 19 which include fuel channels 20 adjacent the anode substrate 16 and air (or other oxidant) channels 21 adjacent the cathode substrate 17 .
  • the reactant gases in the channels 20 , 21 diffuse through respective substrates 16 , 17 ; hence the reference to gas diffusion layers (GDLs).
  • Adjacent a cooler plate 9 the fuel flow channels 20 may be formed in a fuel flow field plate 23 which does not have air flow channels therein; similarly for the cathode side.
  • non-porous and hydrophobic as used herein with respect to the separator plates 19 , mean that the separator plates 19 are sufficiently non-porous and hydrophobic so that substantially no liquid electrolyte penetrates the separator plates.
  • the traditional phosphoric acid fuel cell has a substrate 16 adjacent the anode catalyst 12 which is of substantially the same thickness as the substrate 17 adjacent the cathode catalyst 13 .
  • the acid that is required for operation of the fuel cell, which must sustain the fuel cell for the life thereof, is ideally sealed within the fuel cell at the time of manufacture.
  • the initial acid fill at manufacture is about 35% to 45% of the void volume in both substrates.
  • the life of a phosphoric acid fuel cell is dependent upon the acid being sufficient so that the matrix and seals in substrates are essentially full during operation and is therefore dependent on retaining acid. If the separator plate assemblies 19 are non-porous and hydrophobic, the phosphoric acid required for the life of the fuel cell must be stored within the porous anode and cathode substrates. Because the substrates 16 , 17 represent the principal thermal resistance between the coolers 9 , substrates as thin as possible are desired to minimize the temperature rise within the cells between the coolers, and thereby maximize the power density of the fuel cell stack as well as to reduce cost.
  • any situation which causes the amount of phosphoric acid to exceed the void volume within the porous substrates 16 , 17 results in expulsion of the acid from the cell. That is, the acid will necessarily flow into either or both of the reactant flow field channels 20 , 21 and eventually into the manifolds and other reactant gas plumbing. This reduces the amount of acid available, thereby fore-shortening the life of the fuel cell, as well as damaging components which may reduce performance and/or further shorten the life of the cell.
  • undiluted phosphoric acid that is, 100 wt % phosphoric acid
  • the acid when diluted to on the order of 70 wt %, the acid will remain a liquid to about ⁇ 30° C. (about ⁇ 20° F.). Therefore, when shipping newly manufactured phosphoric acid fuel cells, they are conditioned by diluting the phosphoric acid from close to 100 wt % to about 70 wt % to prevent freezing of the electrolyte during shipment.
  • the acid fill level should be not much greater than about 66%. Any further reduction in available pores will result in diffusional losses which cause unacceptable, reduced performance. It has also been found that the electrolyte cannot be conditioned to about 70 wt % acid without the acid fill level in the anode exceeding the void volume of the anode substrate, resulting in acid expulsion into the reactant gas systems. In fact, conventional phosphoric acid fuel cells having an average initial fill of 40% will result in a 119% acid fill of the anode substrate when diluted to shipping concentration. This of course results in acid expulsion and consequential reduced life of the fuel cell system.
  • the thickness of the anode substrate (GDL) is measurably thicker than the cathode substrate (GDL), preferably at least 1.75 times, and more preferably between about 1.75 and about 3 times thicker than the thickness of the cathode substrate (GDL).
  • the anode substrate is twice the thickness of the cathode substrate, and has an acid fill level of 93.6% of the void volume at the shipping concentration, it will have a fill level of about 55% during operation, which is very good from a fuel diffusion and anode performance point of view.
  • the acid management characteristics of proton-conducting liquid electrolyte fuel cells which utilize non-porous, hydrophobic flow fields are improved while not changing the combined thickness and cost of the anode plus cathode diffusion layers (GDLs).
  • GDLs cathode diffusion layers
  • FIG. 1 is a simplified schematic illustration of a phosphoric acid fuel cell stack known to the prior art.
  • FIG. 2 is a fragmentary, simplified side elevation view of a pair of fuel cells and a cooler plate in a phosphoric acid fuel cell stack known to the prior art, not to scale, with sectioning lines omitted for clarity.
  • FIG. 3 is a fragmentary, simplified side elevation view of a pair of fuel cells and a cooler plate in a phosphoric acid fuel cell stack, not to scale, with sectioning lines omitted for clarity.
  • FIG. 4 is a table illustrating exemplary estimated features of phosphoric acid substrates.
  • a phosphoric acid fuel cell 8 a is configured to employ a proton conducting liquid electrolyte, such as: phosphoric acid; or a mixture of phosphoric acid with either a fluorinated compound or siloxanes; or a liquid in which the anion is a fluoroborate or a fluoroheteroborate.
  • the fuel cell 8 a comprises a substrate 16 a (GDL) adjacent to the anode catalyst 12 which is between about 1.75 and about 3 times as thick as the substrate 17 a adjacent to the cathode catalyst 13 .
  • FIG. 3 is not to scale, the depiction of the anode substrate is substantially three times larger than the depiction of the cathode substrate.
  • the separator plate assembly 19 is preferably configured in a manner similar to that disclosed in WO2006/071232, which is incorporated hereby by reference.
  • FIG. 4 illustrates acid fill as a percent of void volume when the fuel cell is conditioned by dilution to 70 wt % concentration and at substantially 100 wt % concentration, as is the case when operating, for various ratios of anode GDL thickness to cathode GDL thickness.
  • the table of FIG. 4 illustrates that even at a thickness ratio of only 1.5 to 1.0, the diluted fill may still be unacceptably high because it exceeds the void volume of the substrate.
  • the concept herein provides some benefit even if the ratio is near one; that is, providing an anode GDL that is measurably thicker than the cathode GDL will provide some advantage, and be better than a thickness ratio of 1.0 to 1.0.
  • the diluted fill is acceptable because it is less than the void volume of the substrate, and anode performance exceeds necessary performance by an acceptable margin.
  • the diluted fill level is very acceptable and the anode performance has a sufficient margin that additional acid may be added to the cell to prolong its life.
  • the diluted electrolyte fill as a percent of porous substrate void and the margin of improved anode performance can both be made very acceptable.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Fuel Cell (AREA)
  • Inert Electrodes (AREA)
US12/311,592 2006-10-27 2006-10-27 Liquid electrolyte fuel cell having an anode substrate layer thicker than the cathode substrate layer Active 2027-03-01 US8137857B2 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US2006/042495 WO2008051230A1 (fr) 2006-10-27 2006-10-27 Pile à combustible à électrolyte liquide présentant une couche de substrat d'anode plus épaisse que la couche de substrat de cathode

Publications (2)

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US20090325033A1 US20090325033A1 (en) 2009-12-31
US8137857B2 true US8137857B2 (en) 2012-03-20

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US (1) US8137857B2 (fr)
EP (1) EP2160784A1 (fr)
KR (1) KR101300290B1 (fr)
CN (1) CN101542813B (fr)
WO (1) WO2008051230A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110223517A1 (en) * 2011-03-30 2011-09-15 Clearedge Power, Inc. Asymmetric acidification of a membrane-electrode assembly
EP2982000A4 (fr) * 2013-04-02 2016-11-02 Doosan Fuel Cell America Inc Pile à combustible ayant plusieurs couches de substrat d'anode dupliquées
KR102116098B1 (ko) 2014-12-03 2020-05-27 한화정밀기계 주식회사 전자부품 픽업 장치

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20050112449A1 (en) * 2003-11-24 2005-05-26 Mark Mathias Proton exchange membrane fuel cell
US20060263659A1 (en) * 2004-08-31 2006-11-23 Myung-Dong Cho Polymer electrolyte membrane and fuel cell using the polymer electrolyte membrane
US20090053565A1 (en) * 2003-04-22 2009-02-26 Benedetto Anthony Iacovelli Fuel cell, components and systems

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1244165A3 (fr) * 2001-03-19 2006-03-29 Ube Industries, Ltd. Matériau pour base d'électrode d'une pile à combustible
US6677070B2 (en) * 2001-04-19 2004-01-13 Hewlett-Packard Development Company, L.P. Hybrid thin film/thick film solid oxide fuel cell and method of manufacturing the same
KR100647287B1 (ko) * 2004-08-31 2006-11-23 삼성에스디아이 주식회사 폴리머 전해질막 및 이를 채용한 연료전지

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090053565A1 (en) * 2003-04-22 2009-02-26 Benedetto Anthony Iacovelli Fuel cell, components and systems
US20050112449A1 (en) * 2003-11-24 2005-05-26 Mark Mathias Proton exchange membrane fuel cell
US20060263659A1 (en) * 2004-08-31 2006-11-23 Myung-Dong Cho Polymer electrolyte membrane and fuel cell using the polymer electrolyte membrane

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Publication number Publication date
WO2008051230A1 (fr) 2008-05-02
KR20090091704A (ko) 2009-08-28
CN101542813A (zh) 2009-09-23
EP2160784A1 (fr) 2010-03-10
US20090325033A1 (en) 2009-12-31
CN101542813B (zh) 2012-10-10
KR101300290B1 (ko) 2013-08-28

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